diff --git a/vlib/builtin/js/map.js.v b/vlib/builtin/js/map.js.v
index 49cead84e5..94a88a5e0e 100644
--- a/vlib/builtin/js/map.js.v
+++ b/vlib/builtin/js/map.js.v
@@ -8,11 +8,11 @@ pub:
 
 fn (mut m map) internal_set(key JS.Any, val JS.Any) {
 	//$if es5 {
-	#if ('$toJS' in key) key = key.$toJS();
+	#if (key.hasOwnProperty('$toJS')) key = key.$toJS();
 	#if (!(key in m.val.map)) m.val.length++;
 	#m.val.map[key] = val
 	/*} $else {
-		# if ('$toJS' in key) key = key.$toJS();
+		# if (key.hasOwnProperty('$toJS')) key = key.$toJS();
 		# m.val.m.set(key,val);
 	}*/
 	_ := key
@@ -22,10 +22,10 @@ fn (mut m map) internal_set(key JS.Any, val JS.Any) {
 fn (mut m map) internal_get(key JS.Any) JS.Any {
 	mut val := JS.Any(unsafe { nil })
 	//$if es5 {
-	#if (typeof key != "string" && '$toJS' in key) key = key.$toJS();
+	#if (typeof key != "string" && key.hasOwnProperty('$toJS')) key = key.$toJS();
 	#val =  m.val.map[key]
 	/*} $else {
-		# if ('$toJS' in key) key = key.$toJS();
+		# if (key.hasOwnProperty('$toJS')) key = key.$toJS();
 		# val = m.val.m.get(key)
 	}*/
 	_ := key
@@ -34,11 +34,11 @@ fn (mut m map) internal_get(key JS.Any) JS.Any {
 
 #map.prototype.get = function (key) { return map_internal_get(this,key); }
 #map.prototype.set = function(key,val) { map_internal_set(this,key,val); }
-#map.prototype.has = function (key) { if (typeof key != "string" && '$toJS' in key) { key = key.$toJS() } return key in this.map; }
+#map.prototype.has = function (key) { if (typeof key != "string" && key.hasOwnProperty('$toJS')) { key = key.$toJS() } return key in this.map; }
 // Removes the mapping of a particular key from the map.
 @[unsafe]
 pub fn (mut m map) delete(key JS.Any) {
-	#let k = '$toJS' in key ? key.$toJS() : key;
+	#let k = key.hasOwnProperty('$toJS') ? key.$toJS() : key;
 
 	#if (delete m.val.map[k]) { m.val.length--; };
 
diff --git a/vlib/v/gen/js/builtin_types.v b/vlib/v/gen/js/builtin_types.v
index b7de31a0cb..a991a833ca 100644
--- a/vlib/v/gen/js/builtin_types.v
+++ b/vlib/v/gen/js/builtin_types.v
@@ -494,7 +494,7 @@ fn (mut g JsGen) gen_builtin_type_defs() {
 					typ_name:      typ_name
 					val_name:      'map'
 					default_value: 'new map({})'
-					constructor:   'this.map = map; this.length = 0;'
+					constructor:   'this.map = map; this.length = Object.keys(this.map).length;'
 					value_of:      'this'
 					to_string:     'this.map.toString()'
 					eq:            'new bool(vEq(self, other))'
diff --git a/vlib/v/gen/js/tests/map.v b/vlib/v/gen/js/tests/map.v
index 71ba844fc2..4b755390fc 100644
--- a/vlib/v/gen/js/tests/map.v
+++ b/vlib/v/gen/js/tests/map.v
@@ -24,8 +24,8 @@ fn map_any[T](items []T, cb fn (item T) bool) bool {
 	return false
 }
 
-fn test_map_values_method() {
-	// testing map[int]stirng
+fn test_values_method() {
+	// testing map[int]string
 	items_1 := {
 		1: 'item_1'
 		2: 'item_2'
@@ -84,7 +84,7 @@ fn test_map_values_method() {
 	})
 }
 
-fn test_map_values_method_with_generic_constraints() {
+fn test_values_method_with_generic_constraints() {
 	// test with string constraint
 	string_map := {
 		'first':  'hello'
@@ -106,7 +106,17 @@ fn test_map_values_method_with_generic_constraints() {
 	assert int_result.contains(2)
 }
 
-fn test_map_keys_method() {
+fn test_keys_method() {
+	// testing map[int]string keys
+	items_1 := {
+		1: 'item_1'
+		2: 'item_2'
+		3: 'item_3'
+	}
+	for key in items_1.keys() {
+		assert 'item_${key}' == items_1[key]
+	}
+
 	// testing map[string]int keys
 	items_2 := {
 		'item_1': 1
@@ -147,7 +157,7 @@ fn test_map_keys_method() {
 	assert point_keys.contains('unit_y')
 }
 
-fn test_map_keys_method_with_generic_constraints() {
+fn test_keys_method_with_generic_constraints() {
 	// test with string values
 	string_map := {
 		'first':  'hello'
@@ -176,9 +186,51 @@ fn test_map_keys_method_with_generic_constraints() {
 	assert empty_keys.len == 0
 }
 
-fn main() {
-	test_map_values_method()
-	test_map_values_method_with_generic_constraints()
-	test_map_keys_method()
-	test_map_keys_method_with_generic_constraints()
+fn test_direct_map_access() {
+	// testing map[int]string
+	items_1 := {
+		1: 'one'
+		2: 'two'
+		3: 'three'
+	}
+	assert items_1[1] == 'one'
+	assert items_1[2] == 'two'
+	assert items_1[3] == 'three'
+
+	// testing map[string]int
+	items_2 := {
+		'one':   1
+		'two':   2
+		'three': 3
+	}
+	assert items_2['one'] == 1
+	assert items_2['two'] == 2
+	assert items_2['three'] == 3
+}
+
+fn test_map_len() {
+	// testing on the fly maps
+	items_1 := {
+		'one': 1
+		'two': 2
+	}
+	assert items_1.len == 2
+
+	// testing empty map length
+	mut items_2 := map[string]int{}
+	assert items_2.len == 0
+
+	// testing dynamic addition map length
+	items_2['one'] = 1
+	items_2['two'] = 2
+	assert items_2.len == 2
+}
+
+fn main() {
+	test_values_method()
+	test_values_method_with_generic_constraints()
+	test_keys_method()
+	test_keys_method_with_generic_constraints()
+	test_direct_map_access()
+	test_map_len()
 }